1. Field of the Invention
The present invention relates to a light conducting unit, an illumination apparatus, and a projection type display apparatus.
Priority is claimed on Japanese Patent Applications Nos. 2003-177947 filed Jun. 23, 2003 and 2003-333548 filed Sep. 25, 2003, the contents of which are incorporated herein by reference.
2. Description of Related Art
As a first background art in the field of display devices, in which the level of needs related to increase in size and increase in resolution is high, a projection type display apparatus such as a liquid crystal projector or a DMD or the like is known as a device which can easily implement such a type of large scale display.
With this type of projection type display apparatus, normally, illumination apparatuses are used in which rod shaped light conducting units are disposed between the light source and the light valves. These illumination apparatuses take advantage of internal surface reflection within the light conducting units, in order to make the intensity of the light which is emitted from the light source uniform over the light valves.
Such a type of illumination apparatus is, for example, disclosed in Japanese Unexamined Patent Application, First Publication No. 2002-268008. The illumination apparatus described in this document includes a light source which emits light, a rod shaped light conducting unit which makes the illumination distribution of the light which has been emitted from the light source uniform, a first lens system which conducts the light which has been emitted from the light conducting unit, a light polarization creation section which emits polarized light which has a predetermined polarization direction, and a second lens for causing the polarized light which has been emitted from this light polarization creation section to be incident upon a predetermined illumination region.
As described above, a rod shaped light conducting unit is employed with such a conventional illumination apparatus, in order to make the illumination distribution of the light which has been emitted from the light source more uniform. With this type of light conducting unit, the more it is desired to enhance the uniformity of the illumination distribution, the longer is it necessary to make the length of the light conducting unit. However, the problem arises that, when the length of the light conducting unit is made longer, the side and particularly the length of the illumination apparatus become excessive.
Furthermore, in order to reduce the dimensions of the illumination apparatus, the light conducting unit is bent and folded as shown in FIG. 5, then the light, as shown by the arrow sign E in FIG. 5, is reflected in the direction of the light source by the bending and folding portion of the light conducting unit, and, as shown by the arrow sign F in FIG. 5, the light is reflected so as to be emitted at a large emission angle from the light conducting unit, so that it comes to be no longer incident upon the desired illumination region. In other words, there is the problem that, when making the illumination distribution of the light more uniform, the losses become great.
As a second background art, as a light source for a liquid crystal projector, as for example shown in Japanese Unexamined Patent Application, First Publication No. 2000-56266, there exists a device which performs light polarization conversion at high efficiency by, after dividing the light from a lamp into a P polarized light beam and a S polarized light beam, directing these light beams to be incident into one end of a rod integrator, and by converting only the S polarized light in the light which is emitted from the other end of the rod integrator into P polarized light by a phase difference plate which has a spatial distribution and which is disposed at the other end of the rod integrator.
Furthermore, as another type of light source, as for example disclosed in Japanese Unexamined Patent Application, First Publication No. 2000-75407, there exists a device which, along with causing light beams from a pair of lamps to be respectively incident upon a pair of incidence surfaces which are provided to a prism whose vertex angle is approximately 60° and which is formed at an end portion of a rod integrator, also conducts the light into the rod integrator by totally internally reflecting these light beams off the inner side of the opposite incident surfaces.
However, with the above described type of light source, it is not easy to obtain the length of any of the rod integrators. In other words, taking the incident end of the rod integrator as a standard, since the lamps are now disposed in directions which subtend obtuse angles greater than a predetermined angle with respect to the axial direction of the rod integrator, accordingly it is not possible to ensure that the dimensions of the light source with respect to the axial direction of the rod integrator do not become excessively great, so that making the dimensions of the rod integrators long becomes no longer easy. As a result, either the degree by which the rod integrator makes the illumination light more uniform drops below the predetermined desired level, or it is not possible to prevent the overall dimensions of the light source from becoming great, so that the degree of freedom in the design is reduced.
Furthermore, with the above described type of light source, the spatial light modulation element (which is the object of illumination) is arranged in the frontal direction of the emission end of the rod integrator, accordingly, for the same reasons as described above, ether the dimensions of the light source or the dimensions of the projector with respect to the axial direction of the rod integrator become great, so that it becomes no longer easy to lengthen the dimensions of the rod integrator.
The present invention has been conceived in the light of the above described problems, and it takes as its first objective to provide a light conducting unit, and an illumination apparatus and a projection type display apparatus therewith, with which there is no loss of the incident light even though it is bent and folded around, and which can make the illumination distribution of this light more uniform; and the present invention also takes, as its second objective, to provide an illumination apparatus, and a projection type display apparatus which incorporates it, with which, while achieving a sufficiently good uniformization of the illumination light by the rod integrator, also the freedom of design is increased by making the dimensions of the light source more compact, and the like.